you CAN set fan speed. there is an easy and a permanent way by using SSH.
Here is the Easy Way
1.
Use FireFox Browser or Safari if you have a MAC
go to the D3 Miner Configuration/General Settings, screen
Use the inspector to find #fan_control
change "display:none" to "display"

Once that is changed, it will display that Fan option and you can easily change the setting to whatever you want.
I changed mine to 55%
My fans are running at 3960, and my temps are 36-40.
I could have easily gone lower, but my fans are so much quieter now that I don't need to. Even after rebooting, my fan settings stay.


i didn't post the permanent way because I don't want to be responsible for anyone bricking their unit if they aren't familiar with SSH

What about overclocking? I tried overclocking but overclock settings don't apply for some reason.